Jool
Jool is a gas giant and the sixth planet of the Kerbol star system. It is the Jupiter analog for Kerbal Space Program. Aside from Kerbol, Jool has the largest diameter and greatest mass of all celestial bodies. Its extremely high gravity makes orbital maneuvers unpleasantly expensive. While its distance from Kerbin makes it difficult to reach, it is one of the most appealing targets for missions due to its large and complex system of five moons: Laythe, Vall, Tylo, Bop, and Pol. It was possible to land and plant flags on Jool before v0.23. In versions following 0.23, the craft won't stop at an altitude of -100 m, instead it will continue descending until it gets to -250 m. At this point, anything that hits this altitude at any speed will be completely destroyed. In-game description Jool is particularly known for being a rather large, predominantly green planet. Kerbalkind has longed to visit it since it was first spotted in the sky. Philosophers reason that the swirling green planet must be a really nice place to visit, on account of its wholesome coloration. If you look at Jool through a telescope, it is fuzzy. Kerbal Astronomical Society Atmosphere Jool has an extremely dense, cold atmosphere with a mass of approximately 8.8×1019 kilograms, a datum level pressure of 5066.25 kilopascals (50 atmospheres), and a depth of 200,000 meters. Compared to the atmosphere of Kerbin, Jool's atmosphere has 1875 times the mass, 50 times the surface pressure, and nearly 3 times the depth. At an altitude of 91,554 m on Jool, the atmospheric pressure is the same as at sea level on Kerbin (1 atm). The average molecular weight of Jool air is 2.2 g/mol, and its adiabatic index is 1.43. Although the composition of Jool's atmosphere is unknown, these values suggest that it consists mostly of hydrogen and helium. The molar mass of Jool's atmosphere is comparable to the real life planet Jupiter. Because of the low molar weight, Jool air at the datum level is only about 2 times as dense as Kerbin air at sea level. Like all other atmospheres in the game, Jool's atmosphere fades exponentially as altitude increases. The scale height varies with altitude, which is a change from pre-1.0 versions of the game. The pressure-altitude profile is globally constant and independent of temperature. The following table gives the atmospheric pressure at various altitudes above the datum level. Air temperatures decrease as altitude increases up to an elevation of about 123 km, were the coldest atmospheric temperatures are found. A gradual warming begins above 123 km. At an altitude of 194 km there begins a very rapid increase in temperature, suggesting the presence of a thermosphere. As a matter of fact, the temperature of the upper atmosphere is so high that solar panels will actually overheat and explode rather than simply shearing off as they would in other atmospheres. Air temperatures vary with latitude and time of day. At the datum level (elevation = 0) the temperature is a globally constant -73 °C. As the altitude increases, latitudinal and diurnal temperature variations are observed, becoming more pronounced with increasing altitude. At an altitude of 123.45 km, temperatures at the equator vary between a nighttime low of -129 °C and a daytime high of -122 °C. At this same altitude over the poles, the temperature varies between -185 °C and -181 °C. Since Jool has no axial tilt, there are no seasonal temperature variations. Atmospheric flight Since version 1.0.5, Jool's atmosphere is well suited for aerocapture from a high-speed interplanetary intercept. The periapsis altitude required for a successful aerocapture depends on the spacecraft's drag characteristics, its approach velocity, and the desired apoapsis of the resulting orbit. The most effective periapsis for aerocapture is best determined experimentally; however, for a Hohmann transfer originating from Kerbin, it is found that the median value is about 155 km. A Heat shield is required to prevent destructive overheating. Parachutes work very effectively in Jool's dense atmosphere. However, even without parachutes, a craft can reach a relatively low speed, depending on the shape of the ship, as well as its mass. Jool has no solid surface to land on; descending spacecraft will explode when they reach the altitude of -250 m. The message "... collided with Cloud" will be displayed in the mission summary. The game may glitch out and corrupt the save. Prior to version 0.23, it was possible to land on a solid surface, though spacecraft were inevitably and invariably devoured by the Kraken. If a kerbonaut is put on EVA, they will not be destroyed immediately, making one-way sacrificial "landings" possible. However this Kerbal will definitely die, and other glitches may occur, such as the Hell Kraken. Reference frames Natural satellites Trivia * Despite being the Jupiter analog, Jool has roughly the same equatorial radius as the planets Earth and Venus. * The sunsets and sunrises on Jool are purple, and are roughly the same color as Eve's atmosphere. * Like Jool's moons, Jupiter's three nearest moons, Io, Europa, and Ganymede, have relative orbital periods of 1:2:4. Unlike Jool's, Jupiters have differing arguments that result in a true Laplace resonance. * Interestingly, if you use an N-Body simulation, the Jool system is very unstable and will rapidly collapse into a radically different system. Vall gets thrown out into interplanetary space, as do Pol and Bop, and Laythe and Tylo become closer together. In order to solve this problem, the moons must be broken out of resonance, or Jool's mass must be drastically increased. * Jool, Laythe and Tylo all have a surface gravity of 7.85 m/s² (≃ 0.8 g) * The green gas which composes Jool could be chlorine. * Despite not having a surface, the game files that contain what the Kerbals say in the different reports/observations (ScienceDefs.cfg) also contains some reports while landed on the surface of Jool. * Jool is the only planetary body that cannot be "destroyed" by a planet-busting glitch. * According to a post by former KSP developer NovaSilisko, he regrets making Jool intensely green, and speculates that the green color might be algae. * Even if you can land on jool, it would be harder to enter orbit around Eve because of the very dense atmosphere, and that it it much bigger, and needs more delta-V. Also its atmosphere is 200k Km , over 2x the depth. of Eve's. * Jool is the only completely manually colored planet (i.e. it uses a color map instead of procedural height-based coloration) in the stock solar system. This is because it has no terrain, and thus no procedural noise can color it, and it only exists as a ScaledSpace mesh. Mun and Tylo are, however, *mostly* manually colored. Notes Changes ;1.2 * Adjusted datum pressure so crushing pressures are achieved faster. ;1.0 * New atmosphere model, beginning at 200 km instead of 138 km altitude. ;0.18 * Added a new, more distant moon named Pol. ;0.17 * Initial Release Category:Celestials Category:Planets